It has been known for years that dispersion of microfine refractory particles throughout a metal matrix greatly strengthens the metal at elevated temperatures. For example, uniform dispersions of fine thoria were achieved in the products known as TD-nickel and TD-nickel chromium which were produced from chemically precipitated mixtures, reduced to metal powder and consolidated by powder metallurgical techniques. These materials are characterized by high strength at temperatures on the order of 1800.degree.(982.degree. C.) to 2000.degree. F. (1093.degree. C.) but were never successful commercially because the strength at lower temperatures, e.g., 1400.degree. F. (760.degree. C.) or 1600.degree. F. (871.degree. C.), was inadequate.
The provision of metallic materials having continually increasing capabilities in terms of strength and corrosion resistance has been largely directed to the requirements of the gas turbine industry. This industry has been seeking to produce engines having ever increasing capabilities in terms of performance, increased service life and, particularly of late, improved economy in operation. The challenge of the gas turbine industry and, in particular, the designers of blades and vanes for use in the hot end of the gas turbine, has resulted in continual improvement in the properties of metallic materials adaptable for use in gas turbines. Engine designers have been equally adept at improving engine parts to take advantage of improvements in elevated temperature capability afforded by metallurgists and to provide design improvements such as blade cooling. The result has been provision of alloys having improved elevated temperature properties and the provision of engines of even greater capability and reliability.
However, the search for better materials and better engines is never-ending.
With the advent of the mechanical alloying process as described, for example, in U.S. Pat. No. 3,591,362, a new procedure for producing oxide dispersion-strengthened (ODS) metals and alloys which could be adjusted in composition was made available. The process has been adapted to provide ODS nickel-chromium alloys of improved properties, as exemplified by U.S. Pat. No. 3,926,568. Experimental work in developing ODS alloys produced from mechanically alloyed powder has revealed that the process has its own unique limitations and requirements. For example, it has been confirmed that such ODS alloys must be capable of developing a coarse, elongated grain structure in order to obtain good elevated temperature properties therein.
The alloy emanating from U.S. Pat. No. 3,926,568 has been named "MA 6000 E". While the alloy has excellent properties, even higher strength properties are desired. The present invention provides an ODS alloy produced from mechanically alloyed powder which provides such improved strength properties.